The aim of this project is to utilize competence induction for natural genetic transformation in Streptococcus gordonii as a model system for global genetic regulation in the oral streptococci. We also are interested in the determination of what role genetic transformation may play in the horizontal transfer of genetic information within the streptococcal compartment of the oral microbiota and whether intergeneric transfer of resistance or virulence determinants can occur in the plaque ecosystem. Specifically this project involves the following: 1) Isolation and competence mutants of S. gordonii Challis via transposon mutagenesis with which to identify and isolate new competence genes. 2) Promoter characterization of these new genes to identify competence specific controlling elements and regulatory proteins. 3) Elucidation of regulatory circuits based on the promoter analysis and identification of environmental factors modulating competence in the oral environment. 4) Determination of transformation efficiencies between specific tester strains during cocultivation on implantable enamel chips in vivo.